1. Field of the Invention
The present invention relates to a semiconductor device and the manufacturing method thereof.
2. Description of the Related Art
A thin film transistor used for a semiconductor device is required to have different properties according to the object and the function of the semiconductor device. It is important to control the properties of the thin film transistor to satisfy the requirement, and the technique for manufacturing the thin film transistor to have a property appropriate for the intended use has been researched (for example, refer to the patent document 1: Japanese Patent Laid-Open No. H9-27624).
In the patent document 1, a thin film transistor containing an impurity region having a lightly doped drain (LDD) structure is formed using a side wall, thereby making leak current small in OFF-state of a thin film transistor.